Booster ignition compositions for small arms weapon containing boron and boron compositions



fid States Patent Int. Cl. C06c 1/00 US. Cl. 149-22 1 Claim ABSTRACT OFTHE DISCLOSURE The invention relates to improvements in a boostermaterial for igniting substantially instantaneously the full length of aperforated rocket propellant. The booster comprises a mixture of 36%potassium nitrate and 64% of a mixture of aluminum in fine grains withan oxide of a chemically weaker metal as approximately 53% of theformula plus about 40% boron chlorate, 2% boron (90-92% pure), and 5%nitrocellulose binder.

This invention relates to miniature rockets suitable for anti-personneluse and other uses and it relates more particularly to a low cost, lightweight self-propelled rocket of small dimension capable of attainingsuch high velocity as to enable it to be used as an extremely eflicientkinetic energy kill mechanism or for use as other weaponry.

This application is a divisional application of my copending applicationSer. No. 435,780, filed Feb. 11, 1965, entitled Small Arms Weapon, whichis a continuationin-part of application Ser. No. 141,237, filed Sept.20, 1961, which was a continuation-in-part of application Ser. No.61,017, filed Oct. 6, 1960, the latter two applications now abandoned.

This invention relates to a novel ordnance weapon and methods forconstructing the same. According to the basic concept of the weapon, asmall rocket is provided for use as an antipersonnel kinetic energy killmechanism. In accordance with various embodiments of the invention aplurality of such miniature rockets may be packaged together in a firingtube so that many may be fired simultaneously, or a number of suchrockets may be dispersed and fire from a carrier such as a shell, bomb,or missile.

Traditionally, the rifle has been used as the standard small armsweapon. However, it suffers from a number of disadvantages. It isexpensive to manufacture. The accuracy required in machining the barrel,and the precision required in the parts for feeding and aligning thebullet and cartridge, are costly such that providing a means for firinga bullet is considered to be relatively expensive. A rifle is heavy bothin itself and with respect to its ammunition, and it requiresconsiderable skill to manipulate with any degree of effectiveness. Thelength of the barrel and the precision and rifling embodied in thebarrel lining obviously require the rifle to be of a size which makesconcealment difficult, and calls for a rifle of substantial weight,thereby imposing burdens on personnel using it. Further, the bullet hasthe undesirable characteristic of having its maximum velocity at themuzzle of the gun with continual deceleration thereafter, whereas onewould prefer to have the maximum velocity in the probable target zone.Since it is necessary that a bullet must acquire its velocity from theexpansion of gases while in the barrel of the rifle, and prior toejection from the gun, it is essential for the proper design of a rifleto provide a barrel of suflicient length to enable full acceleration ofthe bullet before it emerges from the barrel. The barrel must be formedwith suitable rifling to direct the bullet accurately at the time it isejected from the barrel toward the target. The velocity of the riflebullet from the very start is too low for maximum effectiveness since,using ordinary techniques, the velocity is about 2,800 feet per second.If velocities of 3,000 feet per second and higher can be achieved, thevictim suffers severe shock and tissue damage as contrasted to merepenetration achieved by an ordinary rifle. Even less effectiveness isexperienced in proportion to the distance the bullet travels from therifle before striking a target. Although attempts have been made toobtain higher muzzle velocities for rifles, such attempts haveinvariably resulted in increased weapon weight and rapid erosion of thegun barrel.

Further, the rate of acceleration required to be effected within thelength of the rifle barrel introduces a considerable amount of recoil inthe rifle. The user is thereby exposed to a rather large kick-back whichmakes it diflicult to control the barrel and its effective use islimited to persons capable of absorbing the shock. Further, because ofthe high rate of acceleration and rotation of the bullet projected fromthe rifle, it is difficult to bond or join other elements with thebullet, such as CBR (chemi cal, biological or radiological) agents,which also must be easily disseminated in the target, for delivery withthe bullet to a distant target. This factor therefore limits the rifleto uses for delivery of bullets and like payloads.

Still further, the rifle is subject to the deficiency that once thebullet is free of the barrel, it thereafter loses velocity such thatmaximum elfectiveness, from the standpoint of speed or velocity, occursclosest to the rifle, whereas at distances 200 to 300 yards from therifle, the velocity of the bullet has decreased to such extent as to nolonger have ultimate effectiveness.

In contrast to the rifle and bullet, self-propelled miniature rockets,to which this application is addressed, can he launched by the user withonly a small initial velocity and unlike a rifle the launching deviceneed not be fabricated of high strength, relatively heavy, accuratelymachined elements. Instead, the miniature rocket of this invention canbe launched from any inexpensive and readily available device such as asoda straw, a cigarette, or any elongated tube suitable for impartingdirection to the rocket. Because of the nonlimiting character of thelaunching device, as will hereinafter be described, full and completeconcealment of the rocket and launcher becomes possible thereby torender rockets more effective as a protective device, or as anoffensive/ defensive, or clandestine weapon of war.

Since the rockets are of such small dimension and weight, a series ofrockets or a plurality of rockets can be housed within a singlelaunching device for sequential firing, or for substantiallysimultaneous firing, for coverage over troop concentration area. Theentire assembly weighs less than a fraction of a pound and occupies verylittle space.

Because the rocket gathers speed by acceleration in flight, asdistinguished from acceleration within the confined length of a riflebarrel, there is no resulting recoil or kick-back such that the rocketcan be easily controlled and fired with very little, if any, previoustraining. It is only necessary for the operator to learn to aim therocket weapon in the general direction of the target.

Since the rockets continue to accelerate during flight, the maximumvelocity will be achieved in the probable target area at a distance fromthe point of launch. It becomes possible, with the miniature rockets ofthis invention, to develop velocities which exceed 3500 and even 5000feet per second with speeds of better than 3000 feet per secondobtainable 200 to 300 feet from the point of launch. It is known thatabove certain projectile velocities that the kinetic energy of theprojectile is a more important wound ballistic parameter than momentum.Because of the extremely high velocities of these miniature rockets,obtainable in the probable target area, they are very effective kineticenergy kill mechanisms. Rockets have never before been used as a purelyanti-personnel weapon, mainly because they have been too large for sucha use; but also because they have not been accurate enough, they couldnot be made small enough, and they did not fly fast enough. They havetherefore only been used to deliver payloads.

The rockets of the present invention are new and novel in that eminentscientists were very doubtful that the rockets could be made to flyreliably, nor that they could be made to fly fast enough for theintended use as an anti-personnel kinetic energy kill mechanism. Theserockets produce new and unexpected results in that they have been madeto fly fast enough for the intended use, and they are employed in anentirely new concept as a strictly anti-personnel weapon.

These are but a few of the advantages capable of being derived byminiature self-propelled finned rockets which form the subject matter ofthis invention. Other advantages will become apparent hereinafter fromthe description of the invention.

This invention is thus limited to the important field of miniaturerockets having a diameter within the range of to 1 inch and a lengthwithin the range of 1 to 24 inches and preferably to miniature rocketshaving a diameter of less than 4 inch and a length less than 6 inches.The invention is to be distinguished from such self-propelled rocketryas represented by rockets of considerably larger dimensions which arenot designed for, and are impracticable and incapable of being used asantipersonnel kinetic energy kill mechanism.

Miniature rockets of the type described have not been produced merely bysealing down rockets of substantially larger dimensions which aredesigned for non-equivalent use. There are a number of reasons advanced,by those skilled in the art, for the inability heretofore to producesmall diameter finned rockets of high performance as antipersonnelkinetic energy kill mechanisms.

Rockets of small diameter were believed subject to very low efiicienciesand very low specific impulse. This may have been the result of theinability to achieve uniform radial burning of the propellant wherebyimbalances would develop in the thrust to introduce error in thedirection of flight. Such non-uniform burning would also cause exposureof some portions of the motor casing to higher temperatures than otherportions whereby it was necessary to make use of casings of greater wallthickness and weight to prevent case bursting. This results ininefiicient low performance rockets due to the added weight.

The forces existing, by reason of the rates of acceleration, werebelieved by others to tend to collapse the propellant and causemalfunctions, and the erosive burning of the propellant and expected tocause additional m lf nctions.

Since the burning gases are at temperatures in excess as the casing,nozzle, and the like parts might suffer from relatively instantaneousthermal loads thereby causing shock disintegration of the rocketcomponents before burnout of the propellant.

Since larger finned rockets traveling at speeds of over 2000 feet persecond suffer from aerodynamic heating, it was believed that a similarcondition would occur in small rockets and that the amount ofaerodynamic heating would be suflicient to introduce seriousmalfunctions due to the thin lightweight casing which is necessary ifthe rockets are to fly at high velocity.

It was also believed that miniaturization would increase theinconsistencies of ignition and burning which would cause still greaterundesirable elfects on small rockets thereby to render them inconsistentand unreliable in use.

Experiences with inhibitors used in propellants for rockets of largedimension indicated an undesirable tendency by the inhibitors toinactivate a large proportion of the surface of the propellant sotreated. In miniaturized rockets, it was thought that low performancesand ineflicient utilization of propellant would occur by leaving largeamounts of unburned propellant in the rocket combustion chamber.

Further, those skilled in the art were of the opinion that smallaccurately dimensioned propellant grains, and other components, couldnot be produced for eflicient use in miniature rockets.

It was believed that the small nozzles required for rockets of suchsmall dimensions would be subject to a rate of ablation such as wouldcause loss of pressure and cesation of burning whereby the esential highacceleration rates could not be achieved or maintained. When the nozzlea'blates severely, or erodes erratically, the rocket is incapable ofmaintaining direction thereby creating a very erratic rocket with aresulting large course deviation.

It was also believed impractical to make use of a finned rocket sincesuch thin fins would be required as would be unable to withstand thehigh stresses incurred during flight at speeds in excess of Mach 2.

Reliable pyrotechnic fuses and igniters of the small dimensions andoperational certainty required for small rockets of the dimension towhich this invention is addressed were not available and were believedto be technically beyond the skill of the art.

Rocket cases of the small dimensions, stability, and tolerancescontemplated by this invention were not available and were believed tobe incapable of manufacture. The requirement is for uniform, balanced,thin walled casings capable of withstanding thermal load and shock, highaerodynamic heating, and high internal pressures and aerodynamicstresses, for high performance.

It is an object of this invention to produce and to provide a method forproducing miniature rockets having a length less than 24 inches, andmore specifically in the order of 35 mm., and a diameter less than 1inch and more specifically in the order of 3 mm, which are capable ofconstruction in a simple and eflicient manner to overcome the manydifliculties and problems confronting the manufacture and use thereof aspreviously described, and it is a related object to produce, and toprovide for producing, miniature size rockets of the type describedwhich are formed with an internal grain which is an inside-outsideburner or burns uniformly radially from the inner surfaces radiallyoutward to the casing for substantially complete combustion of thepropellant, and which generates gaseous pressures at a rate forcontrolled acceleration of the rocket with little deviation indirection; and which can make use of a nozzle that ablates at a knownand controllable rate for pressure control during burning of thepropellant to achieve proper speed and direction in flight; whichembodies suflicient strength to maintain the elements in the desiredrelationship in the assembly notwithstanding the large forces broughtinto play by the high rates of acceleration, the high temperatures andthermal shock to which the elements are exposed in use, and the highpressures and aerodynamic forces that exist during flight; which iscapable of acceleration to velocities in excess of 5000 feet per second,and which is capable of impact speeds in excess of 2000 feet per secondat ranges of 200 yards or more; which can be launched singly or innumbers from very simple and inexpensive launching devices; which can beconcealed in use thereby to constitute an offensive, defensive,clandestine weapon; which is capable of use in the atmosphere or underwater without loss of efiiciency or reliability; which can be launchedin series or in clusters to achieve a shotgun effect for more effectivecoverage; which can be manufactured in a simple and inexpensive mannerfrom a large variety of materials; which can be adapted for use withvarious types of payloads, and which has acceptable shelf life and canbe packaged for shipment to distant locations in convenient andinexpensive packages for wider dissemination and application of use; andit is a still further object of this invention to produce and to providenew and improved means and devices for launching miniature rockets ofthe type described.

In accordance with the present invention, a miniature rocket is providedwhich is particularly effective against personnel as a kinetic energykill mechanism. The miniature rockets of the present invention areextremely small by comparison with other rockets heretofore produced.Typically, the rockets are dimensioned to have a length within the rangeof 8 to .35 mm. and a diameter of 1 /2 to 3 mm. and weigh from 40 to 300mg. Large numbers of rockets can be packaged in a launcher to form anassembly of low weight and small size. By firing a large number of suchminiature rockets simultaneously from a launching tube, a shotgun effectcan be achieved making it only necessary to point the launching tube inthe general direction of the target. Since no particular skill isrequired, the weapon is particularly adaptable to use in guerrillawarfare and by unskilled military personnel. The maximum velocity canexceed 5000 feet per second and can be achieved within 50 yards of thefiring point. A velocity of 3000 feet per second can be maintained asfar as 200 yards from the firing point. Thus the rockets of the presentinvention comprise an effective, inexpensive weapon of lightweight andsmall dimension which can be employed by unskilled personnel. Similarly,a large num ber of such rockets can be carried by a bomb, missile, orshell for subsequent dispersion and firing to cover a large area.

In the embodiment described, the overall length of the rocket isapproximately 1.4" and the body is A in diameter. If desired, the noseof the rocket can be adapted to carry a payload such as a highexplosive, or CBR (chemical, biological, or radiological) agent.

With this type of rocket, velocities up to Mach 3 have been achieved atburnout. The rocket can penetrate several layers of plasterboard, steelsheet, or wood of substantial thickness, and it is capable of bonefracture.

In the preferred practice of this invention, novelty exists not only inthe rocket per se having dimensions of the type previously described,but also in the means for construction of the rocket elements includingthe easing, the inhibitor and case bonding agent, the propellant grain,the ignition means, the nozzle, the nose piece and fins, and theirmethod of assembly to form a rocket; also in the means for packaging therocket for storage, shipment, and use, and the means for launching therocket or a plurality of rockets, as the case may be, all as willhereinafter be described.

The tubular casing can be formed by continuous extrusion of metal tubingof the desired small diameter and thin wall section. Conventionaltechniques of cutting to size, for the length desired, and shaping theleading end portion to the ogive desired, form a basic rocket case.

The tubing can be closed at the forward end by any one of the typicalmetallurgical forming processes of impacting, spinning, swaging, orcoining to form the nose.

A unique and novel concept of this invention resides in the fabricationof the rocket casing of thin metal foil or sheet stock. For example, atubular rocket casing having an internal diameter of A; inch and alength of 1 /2 inches and a wall thickness of 0.002 inch can befabricated of metal foil, having a width of 1 /2 inches and a thicknessof 0.0003 inch, by winding the foil about a diameter core or mandrel toform six to seven layers which may be secured one to the other toprovide a laminated structure. Such laminations may be joined into anintegral casing by precoating the foil with a pressure-sensitiveadhesive, a quick setting adhesive, or a heat setting adhesive, or bymetal brazing, or gas welding, or by mechanical working for interfacialbonding. In the alternative, the multiple layers can be joined byelectric or ultrasonic welding to produce a body having strength whichexceeds the strength produced from a solid tube of the same metal. Bythe use of ultrasonic welding techniques, which are fast and relativelyinexpensive, a high strength tubular casing having an internal diameterof A3 inch, and a wall thickness of 0.002 inch, can be fabricated of0.001 inch metal foil wound for two complete revolutions about a A; inchdiameter mandrel.

In the fabrication of the tubular casing by the described process oflamination of thin metallic foils, it is possible to incorporate thermalbarriers in the casing between the foil layers, which, at the same time,increase the strength of the casing and the interbonding of the lamina.Such modifications may be achieved by interleaving with thinnon-metallic films of low heat conductivity. Such construction not onlyincreases the strength of the casing but it minimizes the effects ofthermal shock and enables the rocket to run cool for its short burn timethereby enhancing its resistance to bursting from the internallygenerated high temperatures and pressures.

Tubular casings, with or without fins, can also be formed byconventional techniques into tubular members of thicker wall sectionwhereafter the wall sections can be scaled down to the desired dimensionby conventional mechanical processes such as milling, chemical millingprocesses, or by electro-forming with the metal casing constituting oneof the electrodes from which metal is taken into the electrolyte.

A tubular casing of the desired dimension and mass can also befabricated by electro-forming techniques, using such metals as nickel,to produce a casing of exceptionally high strength.

A tubular casing of the desired dimension and mass can also be producedby impact extrusion. Use is made of a small billet of the desired metaland it is impacted with a male member while at ambient low or hightemperature to effect extrusion of a cavity of the desired dimensionfollowed by heat treatment and/or coining, if desired.

When formed of a plastic or resinous material, with or without fiberousor filler materials, the tubular casing can be fabricated, with orwithout fins, by injection, impact, pressure, or by transfer moldingtechniques. Tubular metal combustion chambers can be inserted inside theplastic body to contain the pressure rise of fast burning propellants,although they have not proven necessary in many designs.

Deep drawing of metal casings in the order of 0.0015 inch in thicknessor greater has been successfully practiced with a length to diameterratio in excess of 9 to 1, particularly when use is made of special highproduction deep drawing machines, such as an eyelet machine.

The tubular rocket casings of the described dimensions can be fabricatedof such materials as carbon steels, stainless steels, titanium,magnesium, aluminum and alloys of aluminum, brass, nickel, uraniumalloys, plastics and filled, or loaded resinous or plastic materials.

The nose of the rocket can be formed in various ways and the choicedepends somewhat on the particular nozzle and fin configuration and/orstructure to be used. If a nozzle is lightweight, e.g., formed directlyas part of the casing, or is a lightweight insert, then a heavy nose isnot required for proper balance and the nose can be formed simply aspart of the casing by deep drawing, rolling, etc. But, if a heavy'nozzle is formed or locked into the aft end of a rocket case or heavierthan normal fins are used, then in order to counter-balance the weight,a heavy nose is required. A nose can be formed as a separate portion andlocked into the tubular casing by metal forming techniques or the nosecan be integral to the casing and weight added through the nozzle end.In the case of plastic rockets the weighted nose can be a needle pointedmetal insert.

The rockets of the present invention may be stabilized in flight invarious ways, preferably by the use of fins. It is desirable to providea rocket in which a plurality, suitably three or four, fins extendradially outward from the tail end portion of the casing to guide therocket in flight. Three fins are easier to effect for mass production,and three finned rockets are more easily packed in clusters, but fourfinned rockets are more stable in flight.

The rockets can be flown successfully without inhibitor if uniformlongitudinal ignition of the propellant grain is achieved whereby thepropellant grain burns uniformly and does not expose one portion of theinterior of the rocket case to the heat of combustion or flame frontbefore nearly all of the propellant is burned.

Achieving uniform ignition with consistant regularity is difficult andtherefor a very thin layer of inhibitor is generally employed to keepthe heat from reaching the case. It was quickly determined that thestandard inhibitors used for large rockets are unsatisfactory forminiature rockets in that they penetrate into the propellant and rendera portion or layer of it useless. This unburned propellant is deadweight in small rockets, lowering the rockets efliciency, in addition totaking up valuable combustion chamber space which is at a premium whenworking with rockets of such small size. The standard inhibitors whichare believed to have the effect of killing part of the propellant arethose which use solvents of acetone, ether, ketone, methyl ethyl ketone,or other highly volatile solvents. Some inhibitors which were tried forthe rockets of the present invention have been epoxys and polyesterresins. These worked but had relatively poor bonding characteristics.Plain rubber cement was tried, but the solvent was objectionable due toits inflammability. Titanium dioxide in a latex soluble base paintworked relatively well and it is believed a magnesium oxide soluble basepaint would also work. The best inhibitors have been cellulose acetate,in the form of a spray, dip, or tape, ethyl cellulose, and polyvinylacetate, polyvinyl alcohol, or polyvinyl chloride. A very thin layer isall that is necessary and if it is in the form of a tape which will bondto the propellant it is perfectly acceptable providing it is thinenough. It is possible that many types of tapes having a pressuresensitive surface which will bind to a high explosive surface may proveadequate and a simple solution to the problems.

The propellant grain is generally of a center burning configuration andis positioned inside the casing adjacent the outer wall extendingradially inward terminating short of the central axis thereby providinga central bore through which the combustion gases issue during outwardradial burning of the propellant from the inner surfaces of the casesubstantially simultaneously throughout the length. E-nd burningpropellants have not proven very successful due to the localized heatconcentrations on the case which causes burn through. The inside radialburners provide a layer of propellant which insulates the case from theflame front until the propellant is nearly expended. Inhibitor betweenthe propellant and case also p ovides insulation. b t lowers theeffective propellant 8 mass to total mass ratio. Inside outside burningpropellants have been tried and have been fairly successful because theyburn so fast that the burn period is over and the pressure expendedbefore the case is significantly effected by thermal shock and pressureload. These propellants are effective for short range rockets, but arenot completely consistent due to case burn through problems.

In the practice of this invention, it is preferred to make use of apropellant which is of the double base type and which is quite similarin composition to powders identified commercially by such names asBullseye, Red Dot, etc., with or without additives, although otherhomogeneous propellants can be used.

The propellant is preferably employed as a single monolithic tubulargrain of relatively thick walled cylindrical configuration dimensionedto have an outer diameter corresponding to the inner diameter of thebore of the casing so as to be received in close fitting coaxialrelationship therein.

The cylindrical section is formed into a tubular membar to provide acentral bore for burning the grain radially outward while the combustiongases are exhausted in their entirety through the bore for passagerearwardly from the rocket through the nozzle whereby the rocket isdriven in flight at an accelerating speed.

The monolithic grain can be machined from a solid rod or it can be castor extruded to the desired inside and outside diameters from a liquid orpaste containing the powder particles in a suitable vehicle. It can beformed by hot pressing directly into the rocket casing whereby apreferred intimate mating relationship is made between the outerperiphery of the propellant grain and the inner surfaces of the casingto minimize the necessity for having to utilize an inhibitor andadhesive at the interface. Micro extrusion techniques have been employedsuccessfully in the preparation of propellants for high performanceminiature rockets.

In the assembly of the grain into the tubular rocket casing, use can bemade of a special technique wherein the rocket casing is heated to anelevated temperature in the order of 100200 C. and the propellant grainis cooled to a lower temperature in the order of 0 to 80 C. at the timeof insertion to take advantage of the high thermal coefficient ofexpansion of the grain whereby as the elements return to normaltemperatures, the propellant grain becomes stressed in radialcompression by the embracing rocket casing. This provides for a sealedrelationship between the grain and the casing thereby preventing cracks,defects and passages in the grain for the flame front to proceed alongto reach the case. This obviates some of the problems heretoforeencountered in case burn through. In addition, the intimate compressivecontact between the grain and easing enables the grain to rely on thecasing for support substantially uniformly throughout its surfacethereby to minimize breakdown of the grain under the extremely highpressures and temperatures and acceleration forces existing in flight,Thus the grain is limited to progressive radial burning from the insideout for generation of uniform gaseous pressures in flight.

Alternatively, the monolithic grain can be bonded to the casing by theuse of a suitable adhesive which will adequately tie in the grain to thecasing for support and which will also serve as a retardant or inhibitorto prevent burning of the grain at the outer wall.

Nozzles can be formed in the rearward end portion of the casing by themetallurgical processes of impacting, rolling, spinning, swaging, orcoining to provide a rocket casing which includes one end adapted toreceive a nose piece, the tubular casing forming the combustion chamher,and the integrally formed nozzle. If nozzles are made in this way thenit is possible to have a front loading rocket. Rockets can then bemanufactured less noses and stockpiled with an assortment of desirednoses such as steel needle points, CBR carrier, or high explosives,etc.,

and the proper nose can be selected and inserted when the need isdetermined.

Unless the nozzle is integrally formed with and during manufacturing ofthe casing, as previously described, the nozzle can be separately formedof such materials as solid or powdered metals, plastics, ceramics,and/or synthetic resinous materials which are filled with such materialsas asbestos, glass, metal, or other fibrous elements or fillers,depending upon the end use of the rocket, the rates of nozzle ablationdesired, and the overall design specifications.

Separately formed nozzles can be secured in position in the tail endportion of the tubular casing by means of cements, brazing, welding,such as ultrasonic welding, or by mechanical forming, such as crimping,rolling, or swaging.

Rocket nozzles of the types described can also be formed very simply andinexpensively by the metallurgical process of punching flat sheets ofmetal, plastics, or other sheet material, to the desired outsidediameter. The part or parts can be punched, with or without coining, toform a conical cavity as well as the port. Punch ing or piercingoperations of the type described yield a divergent or expansion cone togive an economically formed and efiicient nozzle.

The rocket can be fuzed by means which are only a few thousandths of aninch in diameter and are located within the cavity of the propellantgrain, preferably extending to the forward end portion thereof. Theyignite the grain uniformly longitudinally to enable the grain to burnefficiently and progressively radially outward. The fuzing of the rocketis extremely more difficult in miniature fin stabilized rockets of thetype represented by the practice of this invention where it may bedesirable for a finite amount of time to lapse between ignition of thefuze and burning of the propellant. Such delays in fusing are desirablewhen the rockets are clustered in bomblets, or other delivery vehicles,to enable the rockets to be dispersed from the carrier andaerodynamically stabilized before ignition. Delay times of severalseconds or even minutes are sometimes desired for some miniature rocketweapon delivery and employment systems.

A typical fuze can be made from a copper wire with a pyrotechniccoating, generally of a low ash material such as can be fabricated ofpropellant wool, granules, flakes, or powder. See copending applicationsSN. 92,963, Rocket Fuse, filed Mar. 2, 1961, and SN. 95,391, IgnitionMethod, filed Mar. 13, 1961. This type fuze has a time delay value whichis controlled by the dimension, composition, and configuration of thefuze. The ignition of the rocket motor is effected by a booster which islocated at the forward end of the grain and is the internal terminal ofthe fuze.

Use can also be made of ignition means and an ignition train fuze systemwhich burns at a predetermined rate through the bore of the grain fromthe nozzle end with the burning being maintained sufficiently cool orinsulated from the propellant so as not to ignite the grain. If a timedelay is not necessary, electrical ignition can be used by employingsmall diameter enamel coated wires having the ends bared, twistedtogether, and embedded in a glob of booster. A layer of inhibitor /2 to1 mil thick, which can be provided on the internal surface of the grain(inside the perforation), prevents the pyrotechnic fuse from prematurelyigniting the propellant before the booster effects uniform ignition ofthe grain. Inhibitor is particularly necessary in the case of time delayfuzes to prevent premature ignition.

The boosteris provided at the forward end of the grain as a part of thefuzing system. While being minute in size it is capable of quicklyliberating a large amount of heat sufficient to uniformly andlongitudinally ignite the grain. A special booster is used and is veryimportant and a novel portion of the invention. It consists of a mixtureof 36% boron potassium nitrate and 64% T hermit as approximately 53% ofthe formula plus about 40% boron chlorate, 2% boron (-92% pure), and 5%nitrocellulose binder. Thermit is the trademark name of a product knownin the trade to be a mixture of aluminum in fine grains with an oxide ofa chemically weaker metal, usually iron. The booster can be formed ofsmall granules, flakes, or powder. A rocket can be lighted by adefiagrating fuze alone if it is hot and fast enough, but it must bevery fast in order to light the propellant relatively simultaneouslyalong its length to prevent subsequent case burn through and/or endburning from uneven ignition.

The booster must be secured at the forward end of the grain within thecombustion chamber. This prevents gases from the fuze from prematurelyejecting the booster out of the rocket and retains the booster in thecombustion chamber for a time long enough for the propellant grain tostart burning properly. Sometimes the fuze and/or booster Will eject orbecome ejected from the exhaust end of the rocket before full ignitionhas been achieved to cause the rocket to abort. Such losses may occur asthe result of high acceleration during launch and burning. In order toprevent this from occurring the booster can be secured in the forwardend of the combustion chamber by hooking the fuze over the grain towedge it between the booster and the grain. Any other form of secureattachment will also serve the purpose.

Inhibitor or insulation prevents the fuze running to the booster fromprematurely igniting the propellant in a cone or end burningconfiguration. It is an important parameter that the rocket be ignitedwith pure uniform radial burning. With delay fuzes, the interior portionmay be inhibited for only a part of the length of the interior surface.The booster generates a hot fire which sweeps back through theperforation along the grain penetrating the inhibitor layer and causinguniform ignition. The booster is in globular form, not necessarily incontact with the propellant grain. It must be of enough quantity toignite the propellant through the inhibitor but not enough to detonatethe propellant and thereby blow the case.

The miniature rockets of this invention may be used for variouspurposes. The rocket is basically adapted for use as an antipersonnelkinetic energy kill mechanism in the light of the high velocities whichare reached shortly after launch and which can be maintained at rangesof hundreds of yards. The head of the rocket can be provided with a highexplosive charge to impart tremendous physiological shock to the victim.Only very small amounts are necessary to effect this. The payload can beformulated to include CBR agents, incendiary materials, smoke generatingmaterials, chaff for radar detection and jamming, or the like.

A plurality of such rockets can be packed in a bomblet preferably whilethe fins are folded circumferentially about the casing to conservespace. The rockets can also be packaged into containers or bombletsequipped with a flash or heat-generating mechanism which will ignite aflash or heat sensitive portion of the rockets. The flash sensitivecompound is usually applied to the nozzle dis charge portion and has thefuze embedded therein. The compound receives the fire and ignites thefuze initiating the fire train which may have a delay elementincorporated therein. This fiash sensitive compound, a new and novelcomposition, is formed of a mixture of approximately 66% PotassiumChlorate and 34% Lead Thiocyanate as 7580% of the mix plus approximately20% Zirconium powder and about 5% nitrocellulose binder. The proportionscan be varied slightly without effecting the sensitiveness of thecompound.

In the above described example, the rocket casing is dimensioned to havea thickness of 0.005 inch. Such rockets can readily be accelerated tospeeds of over 3300 feet per second in flight. When traveling at a speedof 2300 to 2700 feet per second, the rocket can penetrate over twentylayers of A2 inch Cellotex with few, if any, distortions to the rocketbody. When traveling at a speed greater than 2700 feet per second,penetration of the same thickness of Cellotex cannot be effected as therocket body becomes crimped and bent on impact and sometimes tumbles.This causes a larger wound and increases antipersonnel effectiveness.

The following description will be with reference to the construction ofa miniature rocket of metal foil in accordance with the practice of thisinvention. For this purpose, use is made of steel or stainless steelfoil of about 00003 inch in thickness. In the production of a rocketcasing designated to have a wall thickness of about 0.002 inch, six toseven layers of the metal foil are wrapped about a mandrel, the outerdiameter of which is dimensioned to correspond to the inner diameter ofthe rocket casing. When fully wound about the mandrel, the layers can besecured by a heat sensitive adhesive thinly applied to the foil.

A sharply pointed metal nose can be inserted onto the front end of thecasing and fastened by crimp forming. The nozzle can be formed by theconventional process of swaging or coining the rearward end of theformed casing. The fins can be formed in advance of the nozzle bysplitting or cutting the outer foil layer and turning the split portionsoutwardly to extend radially from the casing.

Before forming the nozzle, a monolithic tubular shaped grain of a doublebase type propellant, inhibited with latex or water soluable resin, isextruded to proper form, dried, and inserted into the casing with themicro-pyrotechnic fuze and booster positioned inside the grain. The fuzecan be insulated with plastic spaghetti or the grain inhibited on theinterior surfaces for part of its length. The fuze is bared at theforward end and wrapped about the booster to anchor the fuze and boosterwithin the propellant grain cavity during the unstable conditions ofignition and high acceleration.

Since the steel foil of which the casing is formed is resilient incharacter, the fins can be collapsed circumferentially about theperipheral surface of the rocket casing so as to occupy less space inloading or packaging. Any curl that remains after launch will cause therocket to roll during flight for less dispersion. A rocket of the typedescribed can achieve a velocity at burnout exceeding 3500 feet persecond.

When foil of greater thickness is employed to form the rocket casing,the front end of the casing can be processed by impacting or coning toincrease the mass density and to form a very sharp pointed nose. In thismodification, I

the fins are preferably separately formed of steel and ultrasonicallywelded in place onto the outside of the casing at the rearward endportion thereof. In the assembly of the rocket, the casing is heated toelevated temperature of about l00200 C. while the propellant grain ischilled to a temperature within the range of 0 to 80 C. and thepropellant, dimensioned to be received in fitting relationship withinthe casing, is inserted in the casing without any inhibitor or adhesive.

The present invention offers a large number of advantages over the priorart of small arms weapons, such as the rifle and bullets, in addition tothose noted earlier.

The jets maybe fired in various fashions. One may use an igniter and afiring button. The igniter leads to a deflagrating fuse, which has aplurality of branches. Each of the deflagrating fuse branches leads intothe central cavity of one of the rockets. When the button is depressed,the igniter is set off, in turn firing all of the rocketssimultaneously. Other ignition devices can be used such as electricalbridge wires or heater wires.

Due to the absence of any kick-back with rockets, use can be made ofsimple and inexpensive tubular members as launchers, for example, sodastraws, bean shooters, cigarette wrapper sand the like, with the abilityto aim the rocket for a relatively high degree of accuracy at shortranges. This too permits substantially full concealment of the weaponfor use as a defensive or clandestine weapon.

Use can also be made of honeycomb sections for storage of a multiplicityof miniature rockets, for support of the rockets in separated relationin the honeycomb sections, or for sequential or simultaneous firing. Thehoneycomb, formed of paper, metal foil, or the like, thus functionseither as a carrier and/or a launcher in which the rockets are eachseparately housed in separated compartments within a minimum of space.

The cases of the rockets can be made in a number of ways. For instance,they can be deep drawn, electro-formed or extruded. Further, they can bemade in more than one piece. The tube portions can be made individually,and the nose portion separately formed and fastened thereto. Further,the fins may be either formed in place or may be made separately andattached to the case, or they may be extruded with the case. Althoughthe cases are preferably made of a thin strong metal, such as stainlesssteel, they can be made of plastic or combinations of metals, plastics,and resins, e.g., a plastic case can be combined with a metal combustionchamber.

The rockets of the present invention may be stabilized in flight invarious ways including the use of the fins heretobefore described. Onemethod of stabilization is to make the nose heavy as by filling it withmetal. Another method is to use skewed or canted fins or vanedcombustion chamber nozzles so that a rotational movement or spin will beimparted to the rocket in flight. Of course, various combinations of thestabilizing means can be employed.

Various guide means may be used to hold the rockets concentric untilthey leave the launcher tube. Thus, the rocket in the lancher isprovided with short forward canard fins as well as rear fins. Thelaunching tubes can be provided with packing material which serves thesame purpose.

Although it is generally preferred to use standard rocket propellants,other propellants can be used, including high explosives. Thus,compounds such as HMX, which would normally detonate, merely burn whenemployed in small diameter rockets. Thus, compositions normally thoughtof as detonators can be employed as propellants and have the advantagesof high density, high specific impulse, and high burning rates.

As has been pointed out above, the rockets of the present invention arewell adapted for use by unskilled troops. The pattern formed by therockets on leaving the launcher is such that accurate aiming is notnecessary. The instructions for use are so simple that they can be givenmerely by cartoons printed on the launcher. By employing a carrier forthe rockets together with dispersal and firing means, they formexcellent weapons for covering a target of large area, such as dispersedtroops. In addition to defense against personnel they can be used asantiaircraft or underwater weapons and may be used to carry smallpayloads of CBR agents or high explosives. Since the rockets emit lightfor about the first 50 yards of their trajectory, they act as tracersaiding in aiming. Additional tracer material can be added to trace overthe full range. From the foregoing it is obvious that there has beenprovided a unique small arms weapon, which can be manufactured in largequantities at low cost, which can be used by unskilled personnel, andwhich is highly lethal.

As has been previously pointed out, the rockets of the present inventionare of very small size and are of a different order of magnitude thanthe rockets heretofore proposed. Conventional rocket formulas do notapply to their performance so that they do not represent a mere scaledown of existing rockets. For instance, the chamber pressure and burningrate formulas of conventional size rockets do not directly apply tothem. For instance, according to conventional rocket formulas, thechamber pressure far exceeds the bursting strength of the case.

It will be understood that changes can be made in the details ofconstruction and methods of fabrication of the miniature rockets withoutdeparting from the spirit of the invention. The invention is not to belimited, therefore, except as defined in the following claim.

We claim:

1. A booster mixture for effecting uniform ignition of miniature rocketscomprising a mixture of approximately 36% boron potassium nitrate and64% of a mixture of aluminum in fine grains with an oxide of achemically Weaker metal as approximately 53% of the formula plus 14approximately 40% boron chlorate, 2% boron (90-92% 2,990,683 7/1961Walden 149-38 X BENJAMIN R. PADGETT, Primary Examiner US. Cl. X.R.

